Polyamide-polyamide-polyimide and polybenzoxazole-polyamide-polyimide polymer having at least one fluorine-containing linking group

ABSTRACT

The present invention provides polyamide-polyamide-polyimide and polybenzoxazole-polyamide-polyimide polymers derived therefrom with improved processing and film characteristics having incorporated into the polymeric backbone the polymeric condensation residuum of novel aromatic diamino compounds having the formula: ##STR1## wherein A is selected from the group consisting of SO 2 , O, S, CO, C 1  to C 6  alkylene, perfluoroalkylene or perfluoroarylalkylene having from 1 to 10 carbon atoms and a bond directly linking the two aromatic groups, and R is selected from the group consisting of hydrogen, hydroxy and C 1  to C 4  alkoxy. 
     The PA-PA-PI polymers of this invention are prepared by reacting compounds of the above formula alone or admixed with other aromatic diamines, with carboxyphenyl trimellitimide or the acid halide or ester derivatives thereof, alone or admixed with one or more aromatic diacid chlorides and/or one or more aromatic tetracarboxylic acids or anhydrides thereof. Polybenzoxazole-polyamide-polyimide derivatives of such polymers are prepared utilizing compounds of the above formula wherein R is hydroxy or C 1  to C 4  alkoxy, and by subjecting the resulting alkoxy or hydroxy-substituted polyamide-polyamide-polyimide to a dehydrating and cyclizing reaction to form the oxazole linkage which gives rise to polybenzoxazole-polyamide-polyimide polymers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to new fluorine-containing polyamide-polyamide-polyimide polymers and polybenzoxazole-polyamide-polyimide polymers derived therefrom which exhibit improved thermal stability, improved resistance to solvents, good processability, good film-forming properties and good film characteristics.

2. Description of Related Art

Polyimides derived from aromatic diamine and dianhydride monomers are widely used in the aerospace industry and electronics industry because of their toughness, low density, thermal stability, radiation resistance, mechanical strength and good dielectric properties. However, such polyimides are often difficult to process thermally and thin films prepared therefrom are often brittle and lack acceptable optical transparency.

It has been suggested that aromatic polyimides having the hexafluoroisopropylidene linking group in the diamine and/or dianhydride monomer have improved solubility and processing properties. For example, U.S. Pat. No. 3,356,648 to Rogers discloses polyimides prepared from 2,2-bis(4-aminophenyl) hexafluoropropane; U.S. Pat. No. 4,592,925 to DuPont discloses polyimides prepared from 2,2-bis(3-aminophenyl) hexafluoropropane; U.S. Pat. No. 4,111,906 to Jones et al. discloses polyimides prepared from 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane; and U.S. Pat. No. 4,477,648 to Jones et al. discloses polyimides prepared from 2,2-bis[(2-halo-4-amino-phenoxy)phenyl] hexafluoropropane. U.S. Pat. No. 4,592,925 discloses polyimides prepared by reacting 2,2-bis(3-aminophenyl) hexafluoropropane and 4,4'-hexafluoroisopropylidene-bis (phthalic anhydride), also known as 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride.

In addition, U.S. Pat. No. 3,179,635 discloses the preparation of polyamide-polyimide polymers said to have good thermal stability and good film-forming properties which may be prepared by condensing a tetra functional aromatic dianhydride, an aromatic diamine and an aromatic acid halide. Polyamides and polybenzoxazole derivatives thereof based on the condensation product of aromatic diamines and aromatic dicarboxylic acids and their derivatives are disclosed in U.S. Pat. Nos. 3,306,876, 3,449,296 and 4,622,285. U.K. patent application No. GB-2188936A discloses the preparation of polyamides and polybenzoxazole derivatives thereof based on the condensation product of 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane with an aromatic dicarboxylic acid or acid halide, followed by cyclization of the polyamide to form a polybenzoxazole. Similar fluorine-containing polyamides are disclosed in U.S. Pat. No. 3,328,352.

In applicant's co-pending application Ser. No. 076,098, filed in the U.S. Patent and Trademark Office on July 21, 1987, is disclosed hydroxy polyimide polymers which, in the preferred embodiment, are prepared by forming the polymeric condensation product of hexafluoro-2,2-bis(3-amino-4-hydroxyphenyl) propane and 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride. These polymers are particularly useful in the preparation of photoresist compositions.

Polyamide-imide polymers and copolymers are also known in the art. These materials are generally prepared by the condensation polymerization of trifunctional acid monomers such as the 4-acid chloride of trimellitic anhydride and one or more aromatic diamines. Examples of such polyamide-imide polymers are disclosed in U.S. Pat. Nos. 3,347,828, 3,494,890, 3,661,832 and 3,920,612. These polymers may be characterized by extremely good high temperature properties (Tg of about 275° C. or higher), good high temperature stability, good tensile strength at high temperatures, good mechanical properties and good chemical resistance. These polyamide-imides are useful as wire enamel coatings, laminates, molded products, films, fibers impregnating varnishes and in other applications where high thermal stability is required.

One of the problems associated with such polyamide-imide polymers is that they exhibit generally poor flow properties which render them difficult to process, particularly to injection mold or to spin into fibers. These polymers are also relatively hydrophilic and tend to absorb moisture which can effect their clarity, heat stability, processability and electrical properties.

Attempts have been made in the art to improve the flow properties of polyamide-imide polymers. For example, U.S. Pat. No. 4,448,925 discloses including from about 1 to about 10 percent phthalic anhydride into the polymerization recipe to provide polyamide-imide copolymers having improved flow properties. However, this technique for improving flow properties is made at the expense of the heat stability and chemical resistance of the polymer. Yet another method for improving the flow properties of such polymers is to form blends thereof with up to about 10% by weight of a polyamide such as nylon 6 or nylon 66, as disclosed in U.S. Pat. No. 4,575,924. Once again however, such an approach to solving the flow problem is made at the expense of the thermal stability and optical clarity of the resultant polymer blend.

Whereas the above-referred to polyimides, polyamide-polyimide and polybenzoxazole polymers are useful for the utilities disclosed, it is desirable to provide polyamide-polyimide polymers and polybenzoxazole polymers which provide not only superior thermal and thermooxidative stability, but also excellent thermal processability, low moisture uptake, low dielectric constant and good film-forming properties and film characteristics.

SUMMARY OF THE INVENTION

The present invention provides polyamide-polyamide-polyimide (PA-PA-PI) and polybenzoxazole-polyamide-polyimide (PB-PA-PI) polymers derived therefrom having improved processing and film characteristics having incorporated into the polymeric backbone the polymeric condensation residuum of novel aromatic diamino compounds having the formula: ##STR2## wherein A is selected from the group consisting of SO₂, O, S, Co, C₁ to C₆ alkylene, perfluoroalkylene or perfluoroarylalkylene having from 1 to 10 carbon atoms, and a bond directly linking the two aromatic groups, and R is selected from the group consisting of hydrogen, hydroxy and C₁ to C₄ alkoxy.

The pA-pA-pl polymers of this invention are prepared by reacting compounds of Formula I, alone or admixed with other aromatic diamines, with carboxyphenyl trimellitimide or the acid halide or ester derivatives thereof, alone or admixed with one or more aromatic diacid chlorides and/or one or more aromatic tetracarboxylic acids or anhydrides thereof. polybenzoxazole-polyamide-polyimide derivatives of such polymers are prepared utilizing compounds of Formula I wherein R is hydroxy or C₁ to C₄ alkoxy, and by subjecting the resulting alkoxy or hydroxy-substituted polyamide-polyamide-polyimide to a dehydrating and cyclizing reaction to form the oxazole linkage which gives rise to polybenzoxazole-polyamide-polyimide polymers.

DETAILED DESCRIPTION OF THE INVENTION

In the more preferred embodiment of the present invention, the R substituent and the amide linkage in Formula I are interchangeably in the meta or para positions with respect to the A group, and the amino substituent groups are meta or para with respect to the amide linkage.

In the most preferred embodiment of the invention, A is a hexafluoroisopropylidene group ##STR3## or a 1-phenyl-2,2,2-trifluoroethane group ##STR4## and R is hydroxy. Compounds having the structure of Formula I are disclosed in Applicant's copending application Ser. No. 07/321,140 filed in the United States Patent and Trademark Office on even date herewith, the disclosure of which application is incorporated herein by reference.

A preferred embodiment of the pA-pA-pI polymers of this invention may be characterized as a polymer comprising at least one recurring group of the structure: ##STR5## wherein the moieties A and R are as set forth above in Formula I, and n is an integer sufficient to give rise to a polymer having an inherent viscosity of at least 0.1 dl/g as measured from a solution of the polymer in dimethylacetamide at 25° C. at a polymer concentration of 0.5 weight percent.

Another preferred embodiment of this invention relates to polybenzoxazole-polyamide-polyimide polymers comprising at least one recurring group of the structure: ##STR6## wherein A and n are as defined above. These polybenzoxazole polymers are derived from PA-pA-PI polymers of Formula II, wherein R is hydroxy or C₁ to C₄ alkoxy positioned interchangeably at the meta or para positions with respect to the A moiety, which are prepared by cyclization of the amide linkage to form the oxazole linkage.

Also within the scope of polymers of Formulas II and III are copolyamide-polyamide-polyimides and polybenzoxazoles derived therefrom wherein a mixture of the diamine of Formula I and at least one different diamine are copolymerized, such as represented by the formula: ##STR7## wherein (II) represents a single condensed unit of Formula II, D represents the residuum of a different aromatic diamine which may or may not contain an R substituent as defined above on the aryl nucleus, n is as defined above, and (a) and (b) equal the mole fraction of each recurring unit in the polymer chain. Preferred polymers and copolymers of the structure IV are those where the mole fractions of (a) and (b) are:

    a=0.05 to 1.0

    b=0.0 to 0.95;

more preferably

    a=0.5 to 1.0

    b=0.0 to 0.5;

and most preferably:

    a=0.7 to 1.0

    b=0.0 to 0.3

Copolyamide-polyamide-polyimides and polybenzoxazoles derived therefrom within the scope of Formulas II and III may also be prepared where the diamine of Formula I is copolymerized with a mixture of the carboxyphenyl trimellitimide and at least one aromatic dianhydride such as represented by the formula: ##STR8## wherein B represents the residuum of a tetravalent aromatic dianhydride and (II), A, R, a, b and n are as defined above.

The carboxyphenyl trimellitimide monomers useful in the present invention are known materials having the general structure: ##STR9## Trimellitimides which may be used are N-(p-carboxyphenyl) trimellitimide, N-(o-carboxyphenyl) trimellitimide and N-(m-carboxyphenyl) trimellitimide. The method of synthesis of these monomers is disclosed in U.S. Pat. No. 3,377,321 and in J. Appl. Polymer Science. Vol 26, 957-978 (1981). These monomers may be condensed in their acid form or in the form of their lower alkyl or phenyl ester derivatives or their acid halide derivatives. The preferred derivative is the acid chloride and the preferred monomer is N-(p-carboxyphenyl) trimellitimide acid chloride having the structure: ##STR10##

Polybenzoxazoles having a structure analogous to the structures of Formulas IV and V, wherein R is hydroxy or C₁ to C₄ alkoxy positioned interchangeably at the meta and para positions with respect to the A moiety, may be prepared by cyclizing the amide linkage to form the oxazole linkage as set forth above.

Preferred dianhydrides suitable for use in the present invention where copolymers are prepared include benzene and naphthalene tetracarboxylic acid dianhydrides, and diphenyl dianhydrides having the nuclear structure: ##STR11## wherein A is as defined above in Formula I. Most preferred dianhydrides arc those where A is a hexafluoroisopropylidene group or a 1-phenyl-2,2,2-trifluoroethane group.

Illustrative of tetracarboxylic acid dianhydrides which are suitable for use in the present invention are:

1,2,4,5-benzene tetracarboxylic acid dianhydride;

1,2,3,4-benzene tetracarboxylic acid dianhydride;

1,4-bis(2,3-dicarboxyphenoxy) benzene dianhydride;

1,3-bis(3,4-dicarboxyphenoxy) benzene dianhydride;

1,2,4,5-naphthalene tetracarboxylic acid dianhydride;

1,2,5,6-naphthalene tetracarboxylic acid dianhydride;

1,4,5,8-naphthalene tetracarboxylic acid dianhydride;

2,3,6,7-naphthalene tetracarboxylic acid dianhydride;

2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride;

2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride;

2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride;

3,3',4,4'-diphenyl tetracarboxylic acid dianhydride;

2,2',3,3'-diphenyl tetracarboxylic acid dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy)diphenyl dianhydride; bis(2,3-dicarboxyphenyl) ether dianhydride;

4,4'-bis(2,3-dicarboxyphenoxy) diphenyl ether dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy) diphenyl ether dianhydride;

bis(3,4-dicarboxyphenyl) sulfide dianhydride;

4,4'-bis(2,3-dicarboxyphenoxy) diphenyl sulfide dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride;

bis(3,4-dicarboxyphenyl) sulfone dianhydride;

4,4'-bis(2,3-dicarboxyphenoxy) diphenyl sulfone dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy) diphenyl sulfone dianhydride;

3,3',4,4'-benzophenone tetracarboxylic acid dianhydride;

2,2',3,3'-benzophenone tetracarboxylic acid dianhydride;

2,3,3'4'-benzophenone tetracarboxylic acid dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy) benzophenone dianhydride;

bis(2,3-dicarboxyphenyl) methane dianhydride;

bis(3,4-dicarboxyphenyl) methane dianhydride;

1,1-bis(2,3-dicarboxyphenyl) ethane dianhydride;

1,1-bis(3,4-dicarboxyphenyl) ethane dianhydride;

1,2-bis(3,4-dicarboxyphenyl) ethane dianhydride;

2,2-bis(2,3-dicarboxyphenyl) propane dianhydride;

2,2-bis(3,4-dicarboxyphenyl) propane dianhydride;

2,2-bis[4-(2,3-dicarboxyphenoxy) phenyl] propane dianhydride;

2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl] propane dianhydride;

4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy) diphenyl-2,2-propane dianhydride;

2,2-bis[4-(3,4-dicarboxyphenoxy-3,5-dimethyl) phenyl]propane dianhydride;

2,3,4,5-thiophene tetracarboxylic acid dianhydride;

2,3,4,5-pyrrolidine tetracarboxylic acid dianhydride;

2,3,5,6-pyrazine tetracarboxylic acid dianhydride;

1,8,9,10-phenanthrene tetracarboxylic acid dianhydride;

3,4,9,10-perylene tetracarboxylic acid dianhydride;

2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride;

1,3-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride;

1,1-bis(3,4-dicarboxyphenyl)-1-phenyl-2,2,2-trifluoroethane dianhydride;

2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl] hexafluoropropane dianhydride;

1,1-bis[4-(3,4-dicarboxyphenoxy) phenyl]-1-phenyl-2,2,2-trifluoroethane dianhydride;

4,4'-bis[2-(3,4-dicarboxyphenyl)hexafluoroisopropyl] diphenyl ether dianhydride,

and mixtures thereof.

One skilled in the art will recognize that the tetracarboxylic acids and acid-esters of the above-listed dianhydride compounds may also be used to produce the polyimides. These tetracarboxylic acids or derivatives thereof are available or may be prepared by known methods. For example, U.S. Pat. No. 3,847,867 to Heath et al. and U.S. Pat. No. 4,650,850 to Howson, which are incorporated herein by reference, show the preparation of bis(ether anhydrides) and bis(dialkyl aromatic ether anhydrides), respectively. The preparation of fluorine-containing dianhydrides is disclosed in U.S. Pat. No. 3,310,573 to Gordon and U.S. Pat. No. 3,649,601 to Critchley et al., which are also incorporated herein by reference.

Copolyamide-polyamide-polyimide copolymers and polybenzoxazoles derived therefrom may also be prepared using a mixture of the diamine of Formula I above and at least one other aromatic diamine having the formula:

    NH.sub.2 --D--NH.sub.2

wherein D is an aromatic moiety of a phenylene, naphthalene or bis-phenylene type compound which may be unsubstituted or ring substituted with halogen, hydroxy, C₁ to C₆ alkyl or C₁ -C₄ alkoxy groups.

Illustrative of diamines which are suitable for use in a copolymerization admixture with the diamine of Formula I include:

m-phenylene diamine;

p-phenylene diamine;

1,3-bis(4-aminophenyl) propane;

2,2-bis(4-aminophenyl) propane;

4,4'-diamino-diphenyl methane;

1,2-bis(4-aminophenyl) ethane;

1,1-bis(4-aminophenyl) ethane;

2,2'-diamino-diethyl sulfide;

bis(4-aminophenyl) sulfide;

2,4'-diamino-diphenyl sulfide;

bis(3-aminophenyl)sulfone;

bis(4-aminophenyl) sulfone;

4,4'-diamino-dibenzyl sulfoxide;

bis(4-aminophenyl) ether;

bis(3-aminophenyl) ether;

bis(4-aminophenyl)diethyl silane;

bis(4-aminophenyl) diphenyl silane;

bis(4-aminophenyl) ethyl phosphine oxide;

bis(4-aminophenyl) phenyl phosphine oxide;

bis(4-aminophenyl)-N-phenylamine;

bis(4-aminophenyl)-N-methylamine;

1,2-diamino-naphthalene;

1,4-diamino-naphthalene;

1,5-diamino-naphthalene;

1,6-diamino-naphthalene;

1,7-diamino-naphthalene;

1,8-diamino-naphthalene;

2,3-diamino-naphthalene;

2,6-diamino-naphthalene;

1,4-diamino-2-methyl-naphthalene

1,5-diamino-2-methyl-naphthalene.,

1,3-diamino-2-phenyl-naphthalene;

4,4'-diamino-biphenyl;

3,3'-diamino-biphenyl;

3,3'-dichloro-4,4'-diamino-biphenyl;

3,3'-dimethyl-4,4'-diamino-biphenyl;

3,4'-dimethyl-4,4'-diamino-biphenyl;

3,3'-dimethoxy-4,4'-diamino-biphenyl;

4,4'-bis(4-aminophenoxy)-biphenyl;

2,4-diamino-toluene;

2,5-diamino-toluene;

2,6-diamino-toluene;

3,5-diamino-toluene;

1,3-diamino-2,5-dichloro-benzene;

1,4-diamino-2,5-dichloro-benzene;

1-methoxy-2,4-diamino-benzene;

1,4-diamino-2-methoxy-5-methyl-benzene;

1,4-diamino-2,3,5,6-tetramethyl-benzene;

1,4-bis(2-methyl-4-amino-pentyl)-benzene;

1,4-bis(1,1-dimethyl-5-amino-pentyl)-benzene;

1,4-bis(4-aminophenoxy)-benzene;

o-xylylene diamine;

m-xylylene diamine;

p-xylylene diamine;

3,3'-diamino-benzophenone;

4,4'-diamino-benzophenone;

2,6-diamino-pyridine;

3,5-diamino-pyridine;

1,3-diamino-adamantane;

bis[2-(3-aminophenyl)hexafluoroisopropyl] diphenyl ether;

3,3'-diamino-1,1,1-diadamantane;

N-(3-aminophenyl)-4-aminobenzamide;

4-aminophenyl-3-aminobenzoate;

2,2-bis(4-aminophenyl) hexafluoropropane;

2,2-bis(3-aminophenyl) hexafluoropropane;

2-(3-aminophenyl)-2-(4-aminophenyl)hexafluoropropane;

2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane;

2,2-bis[4-(2-chloro-4-aminophenoxy)phenyl hexafluoropropane;

1,1-bis(4-aminophenyl)-l-phenyl-2,2,2-trifluoroethane;

1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane;

1,4-bis(3-aminophenyl)buta-1-ene-3-yne:

1,3-bis(3-aminophenyl) hexafluoropropane;

1,5-bis(3-aminophenyl) decafluoropentane;

4,4'-bis[2-(4-aminophenoxyphenyl) hexafluoroisopropyl] diphenyl ether

and mixtures thereof.

Copolyamide-polyamide-copolyimide polymers and polybenzoxazole polymers derived therefrom may also be prepared in accordance with this invention wherein both a mixture of the above diamines and a mixture of the above dianhydrides are reacted.

The polyamide-polyimides of this invention may be prepared by known polymerization techniques, typically by a low-temperature solution condensation method. Suitable solvents include N-methyl pyrrolidone, gamma-butyrolactone, monochlorobenzene tetrahydrofuran and mixtures thereof. The reaction is preferably conducted under substantially anhydrous conditions and for a time and at a temperature sufficient to provide the highest yield of polymer.

The polyamide-polyamide-polyimide polymers containing hydroxy or C₁ -C₄ alkoxy substituents on aromatic carbons adjacent to the amido substituent may be readily converted into the corresponding polybenzoxazole-polyamide-polyimide polymers of this invention by a further dehydrating and cyclization reaction. This reaction is well known and is preferably accomplished by heating the polymer for a sufficient period of time and temperature to cyclize the amido/hydroxy or amido/alkoxy substituent groups to form the oxazole linkage. The preferred method for cyclization is to heat the polyamide-polyimide to a temperature of at least about 300° C. for a period of at least about 1 hour. In general, polyamide-polyamide-polyimide polymers of this invention are soluble in common organic solvents, whereas the derivative polybenzoxazole polymers are not. Thus, where shaped articles such as films or composites are prepared, it is preferred to first cast or mold the desired shape, and then heat the casted or molded shape to form the solvent insoluble polybenzoxazole. In the preferred embodiment of the present invention, the amino and acid based monomers are reacted in approximately equi-molar amounts. The following examples are illustrative in the invention.

EXAMPLE 1

Bis-N,N'-(para-nitrobenzoyl)-hexafluoro-2,2-bis(4-hydroxyphenyl)propane having the following structure is prepared: ##STR12## A 500 ml. round bottom flask equipped with a cooling jacket and mechanical stirrer was charged with 30.0 grams (0.082 mole) of 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane and 400 mls. of acetone. The mixture was stirred until the aminophenyl had dissolved, after which 39.6 grams (0.213 mole) of para-nitrobenzoyl chloride dissolved in 100 mls. of acetone was added dropwise over a period of 30 minutes. The mixture was maintained at less than 20° C. during the addition, after which the mixture was heated with agitation at 35°-40° C. for a period of two hours. 30.0 grams (0.218 mole) of potassium carbonate was then added gradually and the mixture was agitated for two additional hours at 35°-40° C. The heat was removed and the mixture was agitated for an additional 18 hours at room temperature. Thereafter, 20 mls. of water and 16 mls. of a 50% solution of sodium hydroxide was added with vigorous agitation and the mixture was heated at 50°-55° C. for 30 minutes. The heat was then removed and the mixture was transferred to a beaker and the pH was adjusted in the range of 6.0 to 7.0 by addition of HCL (37%) and 500 ml of additional water, added incrementally over a period of 30 minutes under agitation. The mixture was then filtered on an 11 cm. Buchner filter, and the precipitate was washed with water and dried in an oven at 60°-70° C. The yield of bis-N,N'-(para-nitrobenzoyl)-hexafluoro-2,2-bis(4-hydroxyphenyl) propane was 93.6% of theoretical.

EXAMPLE 2

The product of Example 1 was purified by recrystallization in accordance with the following method.

A 1000 ml. round bottom flask equipped with a mechanical stirrer was charged with 51.0 grams of the crude product of Example 1, 316 grams of acetone and 158 grams of methanol.

The mixture was stirred and heated at 40°-50° C. until the product of Example 1 had dissolved. The mixture was cooled to room temperature and 30 grams of Norite was gradually added after which the mixture was stirred for about 25 minutes. The mixture was then clarified by passing it through a 9 cm. Buchner funnel and using a small amount of a 2 to 1 mixture of acetone/methanol as a rinse. The clarified solution was then transferred to a beaker and heated to 50°-55° C. 300 mls. of warm tap water was added dropwise to the solution over a period of 30 minutes, after which the solution was heated to 60°-65° C. After removal from the heat, the solution was allowed to cool slowly to 20°-25° C. which caused a precipitate of the purified compound to be formed. The mixture was filtered using a 9 cm. Buchner funnel, washed with tap water, and oven dried at 60°-70° C. The yield of product was 44 grams which represents an 86.2% recovery.

EXAMPLE 3

This example illustrates the preparation of bis-N,N'-(para-aminobenzoyl)-hexafluoro-2,2-bis(4-hydroxyphenyl) propane by a reduction of the purified product of Example 2. The product prepared according to this Example has the structure: ##STR13## A one liter parr bottle was charged with 20.0 grams (0.03 mole) of the purified product of Example 2, 1.0 grams of a 5% palladium on carbon catalyst and 180.4 grams of ethyl acetate to form a slurry. The slurry was purged by bubbling nitrogen gas through it for 15 minutes. The bottle was then connected to a shaker apparatus capable of maintaining intimate contact between gas, liquid and solid phases, following which the slurry was purged three times with hydrogen gas to insure a pressure tight seal. The shaker was started and the contents were subjected to 50 psi hydrogen gas while heating at 50°-55° C. The mixture was shaken for about 35 minutes. The mixture was then cooled to 35° C. After purging the resulting slurry with nitrogen, it was filtered to remove the catalyst, after which the solvent was evaporated. The product was heated in an air oven at 90° C. until dry, yielding 17.0 grams of dried product. Other dinitro and diamino compounds within the scope of the present invention may be prepared by the processes described above or variations thereof which will be evident to those skilled in the art.

The following example illustrates the preparation of N-(p-carboxyphenyl) trimellitimide acid chloride.

EXAMPLE 4

To a three neck 1 liter flask were charged 46.6 g (0.15 mole) of N-(p-carboxyphenyl) trimellitimide, 150 ml of toluene, 0.5 ml of dimethyl formamide and 28.5 ml of thionyl chloride. The above mixture was heated slowly to 70° C. while monitoring the HCl gas evolution. The temperature was then slowly raised to reflux over a 2 hour period. After gas evolution had ceased, a Dean Stark trap was incorporated into the reaction set up and 72 ml of additional toluene was added. The mixture was then allowed to cool to 55° C. at which time 300 ml of methanol was added dropwise. The reaction mixture was then heated to 60° C. and stirred for 4 hours. The mixture was then cooled to 5° C. and the precipitate was filtered and washed with methanol. The product was obtained in 85.9% yield.

The following example illustrates the preparation of a polyamide-polyamide-polyimide polymer of this invention.

EXAMPLE 5

In a three neck 100 ml flask equipped with a thermometer, condenser, dean stark trap, cooling means, mechanical stirrer and nitrogen inlet tube, and containing 3.02 grams (0.005 mole) of the diamine produced in Example 3 dissolved in a mixture of 25 ml of tetrahydrofuran (THF) and 1 ml of dimethylacetamide (DMAC), was added dropwise a solution of 1.74 grams (0.005 mole) of the N-(p-carboxyphenyl) trimellitimide acid chloride produced in Example 4 dissolved in 35 ml of THF. Dropwise addition was accomplished over a period of 30 minutes with rapid stirring at -10° C. 20 ml of NMp was then added and the solution was stirred for about 18 hours at room temperature. Thereafter the reaction mixture was drowned in 500 ml of methanol while continuing agitation. The polymer precipitated as a white powder which was then filtered and washed with additional methanol. The polymer was dried in a vacuum oven overnight at 110° C.

The resulting PA-PA-PI polymer had the following structure: ##STR14##

The polymer had an inherent viscosity of 0.49 dl/g measured as a 0.5% by weight solution in dimethylacetamide at 25° C., was soluble in most solvents such as THF, NMP and DMAC, and had a glass transition temperature (Tg) of 307° C. The thermooxidative stability of the polymer (the temperature in air at which a 5% weight loss occurs) was 490° C. The specific methods for determining the glass transition temperature and thermooxidative stability are standard techniques as disclosed in copending application D-1276, the disclosure of which is incorporated herein by reference.

EXAMPLE 6

A polybenzoxazole-polyamide-polyimide polymer was prepared by dissolving the polymer of Example 5 in NMp to form a solution which was cast on a glass plate. The coated plate was gradually heated up to about 250° C. to remove the solvent, and then heated to 350° C. for 2 hours to convert the polyamide-polyamide-polyimide to the polybenzoxazole-polyamide-polyimide form. The resulting polybenzoxazole polymer is insoluble in most common solvents, including THF and NM . This polymer has the structure: ##STR15##

The polymers of this invention exhibit improved thermal flow properties and may be melt spun to form fibers and filaments. Because of the good solubility of the PA-PA-PI polymers in common organic solvents, films may be cast from solvent solutions and optionally may be converted to the polybenzoxazole form. Such films may be used as printed circuit backings, insulating dielectric interlayers and other applications where tough, flexible, high temperature stable films having good dielectric properties have been used in the past.

The polymers of this invention may be molded using standard techniques such as compression molding or injection molding to produce melt fabricated articles such as safety masks, windshields, electronic circuit substrates, airplane windows or the like. They may be compounded with graphite, graphite fiber, molybdenum disulphide or pTFE for the production of self-lubricating wear surfaces useful for piston rings, valve seats, bearings and seals. They may also be compounded with fibers such as glass, graphite or boron fibers to produce molding compounds for high strength structural components such as jet engine components. The polymers may also be compounded with friction materials to produce molding compounds for high temperature braking components or with abrasive materials such as diamonds for high speed grinding wheels.

The PA-PA-PI polymers may be cast as films useful as wire and cable wraps, motor slot liners or flexible printed circuit substrates. They may be used as coatings on substrates such as aluminum or silicone dioxide. They are also useful to produce high temperature coatings for magnetic wire, dip coatings for various electronic components, protective coatings over glass, metal and plastic substrates, wire coatings, and photoresist coatings useful in microelectronic processing.

The PA-PA-PI polymers may also be used to produce high temperature adhesives for bonding aerospace structures or electrical circuitry, conductive adhesives when mixed with conductive fillers such as silver or gold for microelectronic applications, or adhesives for glass, metal or plastic substrates.

The polymers may also be used as varnish compositions or matrix resins to produce composites and laminates. The varnish compositions and matrix resins may be used to impregnate glass or quartz cloth, or graphite or boron fibers, for the production of radomes, printed circuit boards, radioactive waste containers, turbine blades, aerospace structural components or other structural components requiring high temperature performance, non-flammability and excellent electrical properties.

It is to be understood that the above-described embodiments of the invention are illustrative only and that modifications throughout may occur to those skilled in the art. Accordingly, this invention is not to be regarded as limited to the embodiments disclosed herein, but is to be limited as defined by the appended claims. 

What I claim is:
 1. A polyamide-polyamide-polyamide polymer comprising at least one recurring group of the structure: ##STR16## wherein A is selected from the group consisting of SO₂, O, S, CO, C₁ to C₆ alkylene, ##STR17## or A represents a bond directly linking the two aromatic groups, R is selected from the group consisting of hydroxy and C₁ to C₄ alkoxy, said polymer having an inherent viscosity of at least 0.1 dl/g as measured from a solution of the polymer in dimethylacetamide at 25° C. at a polymer concentration of 0.5 weight percent.
 2. The polymer of claim 1 wherein the radical A is ##STR18##
 3. The polymer of claim 2 wherein the radical A is ##STR19##
 4. The polymer of claim 3 wherein R is para and the amido linkages are meta with respect to the A group.
 5. The polymer of claim 4 wherein R is hydroxy.
 6. The polymer of claim 4 wherein the imido linkages are para with respect to each amido linkage.
 7. A solvent solution of the polymer of claim
 1. 8. A dried film comprising the polymer of claim
 1. 9. A polybenzoxazole-polyamide-polyimide polymer comprising at least one recurring group of the structure: ##STR20## said polymer prepared by cyclizing: the polymer of claim
 1. 10. The polymer of claim 9 wherein the radical A is ##STR21##
 11. The polymer of claim 10 wherein the amido linkages are meta with respect to the A group.
 12. The polymer of claim 10 wherein the imido linkages are para with respect to each amido linkage.
 13. A dried film comprising the polymer of claim
 9. 